For sealing a hole in a container such as a wine barrel, it is desirable to provide a bung which cannot be easily removed from the hole as a result of unintentional contact or as a result of increased pressures within the container, but which may be readily removed when it is desired to do so. The prior art has provided bungs where the surface contact area between the bung and the surface of the container defining the bunghole is relatively large. The arrangement of prior art bungs has typically resulted in a situation where a relatively small amount of force is required to disengage the bung from the hole, leading to accidental removal (e.g., knocking out) of the bung. Another disadvantage of such a prior art bungs is that conversely a relatively large amount of force is also required to insert and engage the bung with the hole, making insertion difficult.
It may also be desirable to provide an opening through the bung which allows the release of gases from the barrel while also preventing contaminants from entering into the container. Such bungs with pressure release openings are often referred to as stoppers. The prior art has provided various combinations of stoppers and plugs for this purpose.
However, prior art stoppers in such stopper-plug combinations have the same drawbacks as prior art bungs. Also, due to the shape of the barrel, stoppers made of materials such as rubber or silicone are irregularly distorted when inserted, resulting in the through-hole taking on an out-of-round shape. The out-of-roundness can prevent proper operation of the plug/valve used to prevent entry of contaminants.
Accordingly, there remains a need in the art for a bung or stopper which reduces the possibility of unintentional removal from the bunghole, while requiring a relatively small amount of force to be intentionally inserted into and removed. There is a further need for means to eliminate out-of-roundness in the through-hole of deformable stoppers.